Blade ICE G8000 - Manual (Page 76)

RackSwitch G8000 Application Guide
76 „ Chapter 5: Spanning Tree BMD00041, November 2008
Port Priority
The port priority helps determine which bridge port becomes the root/designated port.
The case for the root port is when 2 switches are connected using a minimum of two links with
the same path-cost. The case for the designated port is in a network topology that has multiple
bridge ports with the same path-cost connected to a single segment—the port with the lowest
port priority becomes the designated port for the segment. Use the following command to
configure the spanning-tree port priority (Interface Port mode):
Port Path Cost
The port path cost assigns lower values to high-bandwidth ports, such as 10 Gigabit Ethernet,
to encourage their use. The objective is to use the fastest links so that the route with the lowest
cost is chosen. A value of 0 indicates that the default cost will be computed for an auto-negoti-
ated link speed.
Use the following command to modify the port path cost:
Spanning Tree Group configuration guidelines
This section provides important information on configuring Spanning Tree Groups (STGs):
Changing the Spanning Tree mode
When the spanning-tree mode is changed (for example, RSTP to MSTP),
„ You must reconfigure spanning-tree parameters for each STG, including VLAN assign-
ment.
„ If a STG in RSTP mode is disabled and then re-enabled, the STP topology does not
converge rapidly.
RS G8000 (config-if)# spanning-tree stp 1
priority <0-240, in steps of 16>
RS G8000 (config-if)# spanning-tree stp 1 path-cost <0-200000000>